Anyone know the cheapest way of converting from XT 2×10 to 1×10? Those Sunrace 11-42 cassettes seem a good price, Is there a 30T chainring which will fit the cranks? I can’t seem to find one …

Cheapest way would be to use an extender ring along with a NW chainring. What BCD are the cranks? The 30T NW rings used different chainring bolts BTW to avoid the chain fouling the end of the crank arms.

Superstar 30t will fit, and is cheap

As said, extender ring is cheapest but I think the Sunrace is better (done both).

If you go to 42t then you’ll need to either max out the tension screw on the mech or fit a RADr cage, or use a 11spd mech.

It does quite often work but be warned….
Double cranks sometimes don’t lend themselves so well to conversion to a single ring. You may find the chain protests loudly in the lowest gear because of the chain line.

Triples usually convert ok because the chain ring is centred.

The best option is to get a single ring specific crank.

The Sunrace cassette is an excellent start.

Depends on the cranks. The older 104mm BCD type will happily work with a 30T chainring, as they are often supplied with an offset to clear the chain. I use a Hope narrow wide ring, but there are excellent alternatives.

If you’re using the new M80000 cranks, then the chainring interface is unique to XT/XTR (and soon to be released SLX).

Wow, that was quick. The cranks are 2014 XT.

The cranks are 2014 XT

That’ll be 104mm BCD then, which is good news. You’ll be able to find a narrow wide ring for bobbins which will fit.

All you need then is a new chain, an 11-42 cassette and away you go!